An eye on the back of your head: the Garmin Varia bike radar
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An eye on the back of your head: the Garmin Varia bike radar

Michael Restin
Zurich, on 30.10.2018
Revision: Eva Francis
Obviously, a good light is compulsory when you’re on a bike. But that’s not what the Garmin «Varia RTL510» is all about. Rather than just providing a light, it also keeps an eye on what’s happening behind you so it can warn you about traffic.

The last bike accident I had was after I did a quick shoulder check. There was nothing coming behind me but the car in front braked suddenly. And I only realised when I was clattering handlebars first into the tail lights. Shit happens, even though you’re trying to err on the side of caution. But that’s not really a surprise: whichever way you turn your head means you’re still getting limited field of vision.

The Garmin «Varia RTL510» is designed to increase safety and your view. For a start, there’s the rear light. The battery life offers up to 15 hours in day flash light mode or six hours in standard and night flash mode. It’s certainly bright enough and visible further than the 100 metres required at night in good weather conditions by the regulations in the Swiss technical [requirements for road vehicles](in German) (https://www.admin.ch/opc/de/classified-compilation/19950165/index.html).

During the day, you can even supposedly see it up to 1.6 km (roughly a mile) away. It’s certainly a decent light. But in this instance, that’s almost secondary. The radar feature is what makes the Varia so special. That’s what keeps a lookout on the road behind you.

The bike radar comes with two mounts and a charging cable
The bike radar comes with two mounts and a charging cable

Quick and easy to get to grips with

I use the Varia RTL510 together with Garmin Edge Explore, which lets me control the different light modes and shows the radar warnings on the display. If you don’t have a compatible Garmin device and want to give a fully-fledged bike computer a miss, there’s also the Varia that comes as a bundle with the Varia RDU – a small display that just shows warning messages with bright LEDs.

In both instances, the logic behind it is quick and easy to understand. When a vehicle approaches and is about 140 metres behind you, the device alerts you with a visual and audible warning. A white dot on the edge of the display represents each vehicle. Meanwhile, coloured bars let you know if the car is approaching very fast (red) or at normal speed (orange).

The dots also move to the upper edge of the display at small increments. You’re the dot at the top marked with a specific warning colour. Once the danger has passed, the bars and the dots turn green and another sound gives out the all-clear signal.

What the situation looks like on the Edge Explore display: two vehicles are approaching
What the situation looks like on the Edge Explore display: two vehicles are approaching
Phew, the road behind me is clear again.
Phew, the road behind me is clear again.

Positive user experience

I’m almost slightly surprised at how reliably the warning feature works. There’s no chance of a wheel sucker riding undetected in my slipstream – not even a quiet Tesla can escape my radar. That means I can concentrate on the road in front of me while still knowing what I need to brace myself for in the next few seconds.

Are two, three or even four cars about to overtake me? Or can I cycle more in the centre of the lane to avoid potholes? What about turning – can I switch to the left turning lane without any problems? The Varia RTL510 answers all these questions.

It goes without saying that the Varia doesn’t replace the shoulder check before I pull out or turn. But what it does do is confirm a situation I already know, meaning I can understand it quickly. That’s rather helpful and certainly makes the ride a good bit safer. Thanks to the warning signals, I often already know that a car is approaching before I hear it. And even when I’m using the bike trailer, I can still use the Varia RTL510 without any problems.

Verdict: who needs something like this?

The bike radar is a safety bonus for anyone who rides in road traffic. However, if you cycle through city traffic where it’s bumper to bumper, you probably won’t get as much from it as you would if you were zipping across the countryside on your road bike. Anywhere you can expect (or not expect – that’s the point) speedy overtaking coming out of the blue is a place where Garmin will be your best friend.

The light is visible from a long way away, and the radar gives you a bird’s eye view along with a few seconds’ thinking time without you having to take your eyes off the road ahead. Thanks to the Varia’s slender shape, the device isn’t the thing sticking out a mile even on more delicate bike frames – the only thing standing out is the light.

The oblong 71 g device doesn’t seem bulky or out of place on the seat post. Instead, it looks like it was part of the bike’s overall design. The only thing to watch out for is where you attach it. Make sure it isn’t too low otherwise it can’t see over the back wheel to keep an eye on the traffic. Overall, the Varia RTL510 gets the thumbs up from me. I think it’s a worthwhile investment, especially for sporty cyclists.

The Varia RTL510 shines bright and tucks itself slenderly behind the seat post
The Varia RTL510 shines bright and tucks itself slenderly behind the seat post

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Michael Restin
Michael Restin

Editor, Zurich

Sports scientist, high-performance dad and remote worker in the service of Her Majesty the Turtle.

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